1) Field of the Invention
The present invention relates to a method for producing a nitride semiconductor laser light source that has a long life, and to an apparatus for producing the nitride semiconductor laser light source.
2) Description of the Related Art
Semiconductor laser light sources with short wavelengths of the near-ultraviolet and ultraviolet regions are generally produced by encapsulating a nitride semiconductor laser chip in the inner space of a cap that allows laser light to transmit therethrough, so that the laser chip is shielded from the ambient atmosphere. There is such a problem that at the time of production, contaminants intrude into the inner space of the cap and attach to the facet of the resonator of the laser chip, resulting in deteriorated laser characteristics.
The contaminants mean hydrocarbon compounds and siloxane, often contained in the ambient atmosphere or generated in the course of production of the laser light source and diffused in the production atmosphere. Thus, the contaminants attach to the laser chip and cap during the production of the laser light source, and even if a fresh atmosphere is used when encapsulating the laser chip in the cap, the contaminants cannot be prevented from intruding into the cap to be contained therein.
In some cases, contaminants such as hydrocarbon compounds and siloxane are originally adhered to the constituent members of the laser light source. If the laser light source is produced without any treatment, the contaminants remain inside the cap.
In addition, heat is generated when driving the laser, and because this driving heat causes convection of the contaminants in the encapsulated atmosphere, many of the contaminants are ionized by exposure to short wavelength laser light. The ionized contaminants are adsorbed intensively and strongly to the facet of the laser chip causing the facet of the resonator to deteriorate. This reduces with time the light emission intensity of the laser light source.
To remove the contaminants floating in the encapsulated atmosphere for the purpose of preventing the facet of the resonator from deteriorating, a technique is proposed in Japanese Patent Application Publication No. 2004-14820 such that as shown in FIG. 4, zeolite adsorbent 48 is provided in cap 43 of laser light source 47.
This technique will be described using the drawing. As shown in FIG. 4, semiconductor laser light source 47 has nitride semiconductor laser chip 45, chip-equipped portion 41 for supporting laser chip 45, stem 40 for mounting laser chip 45 thereon, bell-shaped cap 43 having, in a top portion, window portion 44 for laser light to transmit therethrough, and light detecting element 46. Semiconductor laser light source 47 is formed by encapsulating laser chip 45 in a sealed container that is in turn formed by adhering cap 43 to stem 40. On the lower surface of stem 40, electrode lead wires 42 are provided.
However, as a result of a study carried out by the present inventors, it has been found that even when using the above technique, the contaminants in the encapsulated atmosphere cannot be sufficiently removed by adsorption, and when operated for a long period of time, the facet of the laser chip deteriorates.